Review of Aims: The North American Growth in Cerebral Palsy Project (NAGCePP) was developed as a multi-center (4 sites within the United States and 2 sites in Canada) study of growth in cerebral palsy. The identified long-term goals and specific hypotheses for study were delineated into three phases of the project: Phase I: protocol development; Phase II: pilot/feasibility study and Phase III: the formal project: development of growth charts. We have just completed Phase II of the core part of this project, and have submitted abstracts to upcoming meetings based on this pilot anthropological data. The core study was an anthropometric study of growth in a population-based sample of children with CP to which all centers have contributed data. Additionally, individual centers have participated in ongoing nested studies utilizing small sub-samples to which only that individual site (or a few sites) have contributed data. These nested studies have addressed more specific questions related to growth, nutritional status, and their effects on functional status and quality of life. This proposal addresses the nested pilot study of bone mineral density that was initiated at our geographical region (Philadelphia). The specific aims of the Bone Density Nested Study were as follows: 1. To collect pilot data on bone density in a representative, population-based sample of children with CP in four geographic areas in North America. 2. To collect data on risk factors for bone fracture at baseline (e.g. calcium intake, body size, markers of bone mineral metabolism, medications and level of mobility) 3. To collect longitudinal data (by follow-up phone call) on fracture incidence. 4. To compare the results of bone mineral density at the distal femur from children with Cerebral Palsy to healthy children without Cerebral Palsy.